U.S. patent application number 16/607566 was filed with the patent office on 2020-05-07 for system and method docketing a robotic mower.
The applicant listed for this patent is Changzhou Globe Co., Ltd.. Invention is credited to Stefan Strandberg.
Application Number | 20200142425 16/607566 |
Document ID | / |
Family ID | 66190450 |
Filed Date | 2020-05-07 |
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United States Patent
Application |
20200142425 |
Kind Code |
A1 |
Strandberg; Stefan |
May 7, 2020 |
SYSTEM AND METHOD DOCKETING A ROBOTIC MOWER
Abstract
A method and a system for docketing a robotic mower with a
charging station. The system includes a boundary wire and a
charging station loop wherein the boundary wire makes a loop in the
charging station that is narrower than and crosses the charging
station loop. A return signal is received from a control unit
commanding the robotic mower to return to the charging station. The
robotic mower is controlled to follow the boundary wire until the
charging station loop is detected. The robotic mower then follows
the charging station loop until a crossing between the charging
station loop and the boundary wire loop is detected. The robotic
mower is controlled to follow the charging station loop a first
distance, and then continuing to drive the robotic mower in a
direction straight forward for a second distance. When the robotic
mower has moved the second distance it is turned a predefined angle
towards the charging station and controlled to follow the boundary
wire loop until a charging position is reached.
Inventors: |
Strandberg; Stefan;
(Joenkoeping, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Changzhou Globe Co., Ltd. |
Changzhou, Jiangsu |
|
CN |
|
|
Family ID: |
66190450 |
Appl. No.: |
16/607566 |
Filed: |
February 7, 2018 |
PCT Filed: |
February 7, 2018 |
PCT NO: |
PCT/CN2018/075512 |
371 Date: |
October 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A01D 69/02 20130101;
A01D 2101/00 20130101; G05D 2201/0208 20130101; G05D 1/0088
20130101; G05D 1/0265 20130101; G05D 1/0225 20130101; A01D 34/008
20130101 |
International
Class: |
G05D 1/02 20060101
G05D001/02; A01D 34/00 20060101 A01D034/00; G05D 1/00 20060101
G05D001/00 |
Claims
1-21. (canceled)
22. A method performed by a system for docketing a robotic mower
with a charging station, the system comprising the robotic mower
having a control unit and at least one sensor, a boundary wire, a
charging station loop and the charging station and wherein the
boundary wire makes a loop in the charging station that is narrower
than and crosses the charging station loop, the method comprising:
receiving a return signal from the control unit that the robotic
mower shall return to the charging station, controlling the robotic
mower to follow the boundary wire at a distance, detecting the
charging station loop by means of the at least one sensor,
controlling the robotic mower to follow the charging station loop,
in a direction away from the boundary wire, by using at least one
sensor, detecting, by means of the at least one sensor, a crossing
between the charging station loop and the boundary wire loop,
controlling the robotic mower to follow the charging station loop a
first distance after detection of the crossing, continuing to drive
the robotic mower in a direction straight forward for a second
distance, turning, by means of the control unit, the robotic mower
towards the charging station, and controlling the robotic mower to
follow the boundary wire loop with at least one sensor until a
charging position is reached.
23. The method according to claim 22, wherein the robotic mower
follows the boundary wire at a random distance.
24. The method according to claim 22, wherein the first distance
and the second distance are reached when at least one sensor is in
a known position in front of the charging station.
25. The method according to claim 22, wherein the first distance
and the second distance are predetermined distances.
26. The method according to claim 22, wherein the robotic mower
turns towards the charging station until at least one sensor passes
the boundary wire loop.
27. The method according to claim 22, wherein the robotic mower is
provided with two front sensors and one rear sensor and wherein the
detection of the charging station loop is determined when one of
the front sensors passes the charging station loop.
28. The method according to claim 22, wherein the robotic mower is
provided with two front sensors and two rear sensors and wherein
the first distance and the second distance are reached when one of
the two rear sensors reaches the charging station loop and the
boundary wire loop, respectively.
29. A system for docketing a robotic mower with a charging station,
comprising the robotic mower, a boundary wire, a charging station
loop and the charging station and wherein the boundary wire makes a
loop in the charging station that is narrower than and crosses the
charging station loop, the robotic mower further comprising a
control unit and at least one sensor, wherein the control unit
comprises a processor and a memory, the memory comprising
instructions which when executed by the processer causes the system
to: receive a return signal from the control unit that the robotic
mower shall return to the charging station, control the robotic
mower to follow the boundary wire at a distance, detect the
charging station loop by means of the at least one sensor, control
the robotic mower to follow the charging station loop, in a
direction away from the boundary wire, with at least one sensor,
detect, by means of the at least one sensor, a crossing between the
charging station loop and the boundary wire loop, control the
robotic mower to follow the charging station loop a first distance
after detection of the crossing, continue to drive the robotic
mower in a direction straight forward for a second distance, turn,
by means of the control unit, the robotic mower towards the
charging station, and control the robotic mower to follow the
boundary wire loop with at least one sensor until a charging
position is reached.
30. The system according to claim 29, which is further caused to
follow the boundary wire at a random distance.
31. The system according to claim 29, which is further caused to
determine that the first distance and the second distance are
reached when at least one sensor is in a known position in front of
the charging station.
32. The system according to claim 29, which is further caused to
determine that the first distance and the second distance are
predetermined distances.
33. The system according to claim 29, which is further caused to
turn the robotic mower towards the charging station until at least
one sensor passes the boundary wire loop.
34. The system according to claim 29, wherein the robotic mower is
provided with three sensors, two front sensors and one rear sensor
and wherein the system is further caused to determine detection of
the charging station loop when one of the front sensors passes the
charging station loop.
35. The system according to claim 29, wherein the robotic mower is
provided with two front sensors and two rear sensors and wherein
the first distance and the second distance are reached when one of
the two rear sensors reaches the charging station loop and the
boundary wire loop, respectively.
36. A method performed by a system for docketing a robotic mower
with a charging station, the system comprising the robotic mower
having a control unit and at least one sensor, a boundary wire, a
charging station loop, the charging station and at least one guide
wire and wherein the boundary wire makes a loop in the charging
station that is narrower than and crosses the charging station
loop, the method comprising: receiving a return signal from the
control unit that the robotic mower shall return to the charging
station, controlling the robotic mower to follow the guide wire at
a random distance, detecting the charging station loop by means of
the at least one sensor, controlling the robotic mower to move
closer to the guide wire, detecting, by means of the at least one
sensor, that the robotic mower passes the boundary wire loop, and
controlling the robotic mower to follow the boundary wire loop with
at least one sensor until a charging position is reached.
37. The method according to claim 36, wherein the robotic mower is
provided with two front sensors and one rear sensor and wherein the
detection of the boundary wire loop is determined when one of the
front sensors passes the charging station loop.
38. The method according to any of claim 36, wherein both front
sensors are used to control the robotic mower, such that the
robotic mower follows the boundary wire loop to the charging
position.
39. A system for docketing a robotic mower with a charging station,
comprising the robotic mower, a boundary wire, at least one guide
wire, a charging station loop and the charging station and wherein
the boundary wire makes a loop in the charging station that is
narrower than and crosses the charging station loop, the robotic
mower further comprising a control unit and at least one sensor,
wherein the control unit comprises a processor and a memory, the
memory comprising instructions which when executed by the processer
causes the system to: receive a return signal from the control unit
that the robotic mower shall return to the charging station,
control the robotic mower to follow the guide wire at a random
distance, detect the charging station loop by means of the at least
one sensor, control the robotic mower to move closer to the guide
wire, detect, by means of the at least one sensor, that the robotic
mower passes the boundary wire loop, and control the robotic mower
to follow the boundary wire loop with at least one sensor until a
charging position is reached.
40. The system according to claim 39, wherein the robotic mower is
provided with two front sensors and one rear sensor and wherein the
system is further caused to determine detection of the charging
station loop when one of the front sensors passes the charging
station loop.
41. The system according to claim 39, which is further caused to
use both front sensors to control the robotic mower, such that the
robotic mower follows the boundary wire loop to the charging
position.
42. A computer program comprising computer program code, the
computer program code being adapted, if executed by the processers
of the control unit, to implement the method according to claim
22.
43. A computer program comprising computer program code, the
computer program code being adapted, if executed by the processers
of the control unit, to implement the method according to claim 36.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to a system and
method for returning a robotic mower back to a charging station
when a battery of the robotic mower needs to be recharged, and more
specifically for docketing the robotic mower with a charging
station.
BACKGROUND ART
[0002] Robotic mowers, also called self-propelled lawnmowers, are
generally known. These robotic mowers are provided with a
rechargeable battery. When the remaining power in the battery is
below a certain level the robotic mower is programmed to return to
the charging station to recharge the battery. In prior art, there
are many different methods for returning the robotic mower to the
charging station. One common method is that the robotic mower, when
receiving a command to return to the charging station, continues
its movement until a boundary wire is detected and then follows the
boundary wire to the charging station that is provided somewhere
along the boundary wire. When the robotic mower is close to the
charging station a docketing process is started such that the
robotic mower is safely guided into contact with a charging
connector of the charging station.
[0003] U.S. Pat. No. 8,433,468 discloses a robotic mower home
finding system, in which a charging station is connected to an
outer boundary wire loop. The robotic mower comprises a plurality
of sensors for correlating the distance of each sensor to the outer
boundary loop. When the robotic mower is commanded to return to the
charging station it continues its movement until the plurality of
sensors find the outer boundary wire loop and then follows the
outer boundary wire loop along a path that is offset a specified
distance parallel to the outer boundary wire loop. When an inner
wire loop, connected to the charging station, is detected by the
plurality of sensors the robotic mower is turned perpendicular to
the outer boundary wire loop in order to enter the charging
station. The specified distance is changed each time the robotic
mower returns home to the charging station. By varying the specific
distance, damage to the turf along the boundary wire is avoided,
since the robotic mower follows different paths back to the
charging station.
[0004] U.S. Pat. No. 8,942,862 discloses a method for guiding a
robotic garden tool to a predetermined position, i.e. to a charging
station. The robotic garden tool comprises a control unit and a
sensor unit for wirelessly detecting guiding signals. The guiding
signals are generated in guide wires which the robotic garden
follows when it returns back to the charging station. Using guide
wires often enables a shorter and faster way back to the charging
station compared to following a boundary wire. When a first guiding
signal is detected from a first guide wire, the robotic garden tool
follows the first guiding signal at a variable distance from the
first guide wire towards the charging station in response to a
command from the control unit. When a second guiding signal is
detected from a second guide wire the robotic garden follows one of
the first or the second guiding signal at a pre-configured distance
from the corresponding guide wire towards the charging station. The
second guiding signal is detected within a predetermined distance
from the charging station.
[0005] Thus, there are described numerus different ways in prior
art to return a robotic mower to a charging station. However, there
is still room for improvements and especially for the final stage,
i.e. the docketing to the charging station. The problem with the
docketing process is to make an accurate line up of the robotic
mower that ensures that the charging contacts of the robotic mower
will securely attach to the docketing station.
SUMMARY OF INVENTION
[0006] An object of the present invention is to provide a method
for returning a robotic mower to a charging station when the
robotic mower needs to be recharged and where the docketing
process, i.e. the process when the robotic mower is about to dock
with charging contacts in the charging station, is simple and
reliable.
[0007] According to one aspect of the present invention this object
is achieved by a method for docketing a robotic mower with a
charging station, which method is performed by a system comprising
the robotic mower having a control unit and at least one sensor, a
boundary wire, a charging station loop and the charging station and
wherein the boundary wire makes a loop in the charging station that
is narrower than and crosses the charging station loop. The method
comprises receiving a return signal from the control unit that the
robotic mower shall return to the charging station. In response
thereto, the robotic mower is controlled to follow the boundary
wire at a distance until the charging station loop is detected by
means of the at least one sensor. The robotic mower is then
controlled to follow the charging station loop in a direction away
from the boundary wire, by using at least one sensor, until a
crossing between the charging station loop and the boundary wire
loop is detected, by means of the at least one sensor. Thereafter,
the robotic mower is controlled to follow the charging station loop
a first distance after detection of the crossing, and then
continuing to drive the robotic mower in a direction straight
forward for a second distance. When the robotic mower has moved the
second distance it is turned towards the charging station, by means
of the control unit, and then the robotic mower is controlled to
follow the boundary wire loop with at least one sensor until a
charging position is reached.
[0008] In an exemplary embodiment, the robotic mower is controlled
to follow the boundary wire at a random distance.
[0009] In another exemplary embodiment, the robotic mower reaches
the first distance and second distance when at least one sensor is
in a known position in front of the charging station. The first and
second distance are predetermined distances.
[0010] In an exemplary embodiment, the robotic mower turns towards
the charging station until at least one sensor passes the boundary
wire loop.
[0011] In another exemplary embodiment the robotic mower is
provided with three sensors, two front sensors and one rear sensor
and the detection of the charging station loop is determined when
one of the two front sensors passes the charging station loop.
[0012] In yet another exemplary embodiment the robotic mower is
provided with four sensors, two front sensors and two rear sensors
and the first distance and the second distance are reached when one
of the two rear sensors reaches the charging station loop and the
boundary wire loop, respectively.
[0013] Another object of the present invention is to provide a
system for docketing a robotic mower with a charging station when
the robotic mower needs to be recharged and where the docketing
process, i.e. the process when the robotic mower is about to dock
with charging contacts in the charging station, is simple and
reliable.
[0014] According to another aspect of the present invention this
object is achieved by a system for docketing a robotic mower with a
charging station, comprising the robotic mower, a boundary wire, a
charging station loop and the charging station and wherein the
boundary wire makes a loop in the charging station that is narrower
than and crosses the charging station loop, the robotic mower
further comprises a control unit and at least one sensor, wherein
the control unit comprises a processor and a memory, the memory
comprising instructions which when executed by the processer causes
the system to:
receive a return signal from the control unit that the robotic
mower shall return to the charging station, control the robotic
mower to follow the boundary wire at a distance, detect the
charging station loop by means of the at least one sensor, control
the robotic mower to follow the charging station loop, in a
direction away from the boundary wire, with at least one sensor,
detect, by means of the at least one sensor, a crossing between the
charging station loop and the boundary wire loop, control the
robotic mower to follow the charging station loop a first distance
after detection of the crossing, continue to drive the robotic
mower in a direction straight forward for a second distance, turn,
by means of the control unit, the robotic mower towards the
charging station, and control the robotic mower to follow the
boundary wire loop with at least one sensor until a charging
position is reached.
[0015] In an exemplary embodiment, the robotic mower of the system
is further caused to follow the boundary wire at a random
distance.
[0016] In another exemplary embodiment, the robotic mower of the
system is further caused to determine that the first distance and
second distance are reached when at least one sensor is in a known
position in front of the charging station. The first and second
distance are predetermined distances.
[0017] In an exemplary embodiment, the robotic mower of the system
is caused to turn towards the charging station until at least one
sensor passes the boundary wire loop
[0018] In another exemplary embodiment, the robotic mower is
provided with three sensors, two front sensors and one rear sensor
and the system is further caused to determine detection of the
charging station loop is determined when one of the two front
sensors passes the charging station loop.
[0019] In yet another exemplary embodiment, the robotic mower is
provided with four sensors, two front sensors and two rear sensors
and wherein the first distance and the second distance are reached
when one of the two rear sensors reaches the charging station loop
and the boundary wire loop, respectively.
[0020] In yet another exemplary embodiment, the system is further
caused to use both front sensors to control the robotic mower, such
that the robotic mower follows the boundary wire loop to the
charging position.
[0021] Another object of the present invention is to provide a
method, that is simple and reliable, for docketing a robotic mower
with a charging station when the robotic mower needs to be
recharged and the robotic mower uses a guide wire when returning
back to the charging station.
[0022] According to yet another aspect of the present invention
this object is achieved by a method performed by a system for
docketing a robotic mower with a charging station, wherein the
system comprises the robotic mower having a control unit and at
least one sensor, a boundary wire, a charging station loop, the
charging station and at least one guide wire. The boundary wire
makes a loop in the charging station that is narrower than and
crosses the charging station loop. The method comprises receiving a
return signal from the control unit that the robotic mower shall
return to the charging station. In response thereto, the robotic
mower is controlled to follow the guide wire at a random distance
until the robotic mower detects the charging station loop by means
of the at least one sensor. When the charging station loop is
detected, the robotic mower is controlled to move closer to the
guide wire until it is detected, by means of the at least one
sensor, that the robotic mower passes the boundary wire loop. The
robotic mower is the controlled to follow the boundary wire loop
with at least one sensor until a charging position is reached.
[0023] In an exemplary embodiment, the robotic mower is provided
with three sensors, two front sensors and one rear sensor and the
detection of the boundary wire loop is determined when one of the
front sensors passes the charging station loop. In another
exemplary embodiment, both front sensors are then used to control
the robotic mower during the docketing process, such that the
robotic mower follows the boundary wire loop to the charging
position.
[0024] Another object of the present invention is to provide a
system that is simple and reliable and used for docketing a robotic
mower with a charging station when the robotic mower needs to be
recharged and the robotic mower uses a guide wire when returning
back to the charging station.
[0025] According to another aspect of the present invention this
object is achieved by a system for docketing a robotic mower with a
charging station, the system comprises the robotic mower, a
boundary wire, at least one guide wire, a charging station loop and
the charging station. The boundary wire makes a loop in the
charging station that is narrower than and crosses the charging
station loop. The robotic mower comprises a control unit and at
least one sensor, wherein the control unit comprises a processor
and a memory, the memory comprising instructions which when
executed by the processer causes the system to:
receive a return signal from the control unit that the robotic
mower shall return to the charging station, control the robotic
mower to follow the guide wire at a random distance, detect the
charging station loop by means of the at least one sensor, control
the robotic mower to move closer to the guide wire, detect, by
means of the at least one sensor, that the robotic mower passes the
boundary wire loop, and control the robotic mower to follow the
boundary wire loop with at least one sensor until a charging
position is reached.
[0026] In an exemplary embodiment, the robotic mower is provided
with three sensors, two front sensors and one rear sensor and the
system is further caused to determine detection of the charging
station loop when one of the front sensors passes the charging
station loop. In another exemplary embodiment, the system is
further caused to use both front sensors to control the robotic
mower during the docketing process, such that the robotic mower
follows the boundary wire loop to the charging position.
[0027] According to one aspect there is achieved a computer program
comprising computer program code, which computer program code is
adapted, if executed by the processer of the control unit, to
implement the methods described above.
[0028] By providing a method and a system for docketing a robotic
mower with a charging station according to the present invention it
is possible to achieve a reliable yet simple docketing process,
where the robotic mower is safely guided into contact with the
charging contacts of the charging station.
[0029] The solution will also reduce the component costs for a
charging station compared to having separate loop wires for guiding
the mower to a charging position. The reduced number of loop wires
will also reduce the number unique codes that are needed and used
by the system which further reduces the complexity.
BRIEF DESCRIPTION OF DRAWINGS
[0030] The invention is now described, by way of example, with
reference to the accompanying drawings, in which:
[0031] FIG. 1 a schematic view of a robotic mower system.
[0032] FIG. 2a is a schematic view of an exemplary embodiment of
the robotic mower.
[0033] FIG. 2b is a schematic view of another exemplary embodiment
of the robotic mower.
[0034] FIG. 3 is a schematic block diagram of a control unit in the
robotic mower.
[0035] FIG. 4 is a schematic block diagram of a signal
generator.
[0036] FIG. 5a to FIG. 5i show different docketing steps when the
robotic mower docks with a charging station via a boundary
wire.
[0037] FIG. 6a to FIG. 6d show different docketing steps when the
robotic mower docks with a charging station via a guide wire.
[0038] FIG. 7 is a flow chart of an exemplary method for docketing
the robotic mower with the charging station.
[0039] FIG. 8 is a flow chart of another exemplary method for
docketing the robotic mower with the charging station.
DESCRIPTION OF EMBODIMENTS
[0040] In the following, a detailed description of exemplary
embodiments for docketing a robotic mower with a charging station
according to the present invention will be presented.
[0041] FIG. 1 shows a schematic overview of a system for performing
the method of docketing a robotic mower 2 with a charging station
11. The robotic mower 2, or as it also may be called a
self-propelling lawnmower, is battery powered and needs to be
recharged at regular intervals. The robotic mower 2 is during
operation configured to move across an area A surrounded by a
boundary wire 4. As is obvious the robotic mower 2 is depicted
somewhat enlarged for the sake of clarity. The boundary wire 4 may
be configured in many different ways, such that it delimits the
area A within which the robotic mower 2 is allowed to move. The
boundary wire 4 is preferably provided under the ground in the
lawn, such that is not visible, but may also be provide on or above
the ground. The boundary wire 4 could be an ordinary copper wire of
single-core type. There are of course also other options, which are
well-known by a person skilled in the art, such as multi stranded
wire types. As may be seen in FIG. 1 the boundary wire 4 makes a
loop 4a in the charging station 11. This loop 4a will be used to
guide the robotic mower 2 into charging contact with the charging
station 11, which will be described further below.
[0042] The system also comprises the charging station 11 mentioned
above. The charging station 11 is shown with dotted lines in FIG. 1
in order to not unnecessary smudge the figure. The charging station
itself 11 may be seen as the place where the charging of the
robotic mower 2 takes place, but could for an example also be
provided with a charging plate onto which the robotic mower 2 is
guided when performing docketing. A charging plate will make the
docketing process more precise, since the robotic mower 2 will be
at an even and predictable ground during the docketing process. In
order to identify where the charging station 11 is located, there
is provided a charging station loop 10 around the charging station
11. As shown in FIG. 1 the boundary wire loop 4a is narrower than
and crosses the charging station loop 10.
[0043] A system according to the present invention may also as an
option comprise one or more guide wires 8. A guide wire 8 is a wire
that the robotic mower 2 may follow when returning to the charging
station 11. Normally the robotic mower follows the boundary wire 4
back to the charging station 11, which depending on where the
robotic mower 2 starts to follow the boundary wire 4 may be quite a
distance. By using a guide wire 8 it is possible to return the
robotic mower 2 to the charging station 11 in a faster and less
energy consuming way, which is well known in the art.
[0044] The boundary wire 4, the charging station loop 10 and the
optional one or more guide wires 8 are all connected to a signal
generator 6 which feeds each wire and loop with an Alternating
Current, AC, signal, such that the robotic mower 2 may recognize
which wire or loop it is detecting when it is within sensing
distance, which is also known in the art.
[0045] Turning now to FIG. 2a, an exemplary embodiment of the
robotic mower 2 will be closer described. The robotic mower 2
comprises a control unit 22, wheels 20, at least one sensor 12, 14
and/or 16 and a battery 18. The control unit 22, which will be
closer described in conjunction with FIG. 3, comprises among other
things a processor 80 for controlling the movement of the robotic
mower 2. When the robotic mower 2 is in operation the sensors 12,
14 and 16 sense the magnetic field that is generated in the
boundary wire 4, the charging station loop 10 and where appropriate
also the one or several guide wires 8. The sensed magnetic field
(signal) is decoded in the control unit 22 to determine from which
loop or wire it was received. In a preferred embodiment, the
robotic mower 2 is provided with three sensors, two front sensors
12, 14 and one rear sensor 16. In this embodiment one of the two
front sensors 12, 14 may be used to detect the presence of the
charging station loop 10. This configuration may be beneficial for
increasing the precision in the docketing process.
[0046] FIG. 2b shows another embodiment of the robotic mower 2, the
difference to the previous embodiment being that it comprises two
rear sensors 17, 19 instead of one. The rest of the description of
the robotic mower 2 will therefore not be repeated here. With two
rear sensors 17, 19 the precision of the docketing process may be
further enhanced. One or both of the rear sensors 17, 19 may for
example be used when determining that a first distance and second
distance has been reached in relation to the charging station loop
10 and the boundary wire loop 4a, respectively, during the
docketing process as will be further be described below.
[0047] With reference to FIG. 3, the control unit 22 of the robotic
mower 2 will be closer described. The control unit 22 comprises, as
mentioned above the processor 80 and a memory 82. The memory 82 may
comprise a computer program 84 comprising computer program code,
i.e. instructions. The computer program code is adapted to
implement the method steps performed by the robotic mower 2 when
the code is executed on the processor 80. The control unit 22
further comprises an interface 86 for communication with the
sensors 12, 14 and 16, and the sensors 12, 14, 17 and 19,
respectively, and a motor that operates the robotic mower 2.
[0048] The processor 80 may comprise a single Central Processing
Unit (CPU), or could comprise two or more processing units. For
example, the processor 80 may include general purpose
microprocessors, instruction set processors and/or related chips
sets and/or special purpose microprocessors such as Application
Specific Integrated Circuits (ASICs), Field Programmable Gate
Arrays (FPGAs) or Complex Programmable Logic Devices (CPLDs). The
processor 80 may also comprise a storage for caching purposes.
[0049] FIG. 4 depicts the signal generator 6, which also comprises
a processor 60 and a memory 62. The memory 62 may comprise a
computer program 64 comprising computer program code, i.e.
instructions. The computer program code is adapted to implement the
method steps performed by the signal generator 6 when the code is
executed on the processor 60. The signal generator 6 further
comprises an interface 66 for transmitting the generated AC signal
to the boundary wire 4, charging station loop 10 and if appropriate
the guide wire or wires 8.
[0050] As for processor 80 also the processor 60 may comprise a
single Central Processing Unit (CPU), or could comprise two or more
processing units. For example, the processor 60 may include general
purpose microprocessors, instruction set processors and/or related
chips sets and/or special purpose microprocessors such as
Application Specific Integrated Circuits (ASICs), Field
Programmable Gate Arrays (FPGAs) or Complex Programmable Logic
Devices (CPLDs). The processor 60 may also comprise a storage for
caching purposes.
[0051] Turning now to FIG. 5a to FIG. 5i and FIG. 7 exemplary
embodiments of the method according the present invention will be
closer described. The method starts in step S100 in which the
robotic mower 2 receives a return signal from the control unit 22,
which commands the robotic mower 2 to return to the charging
station 11. Step S100 may be triggered by detecting that the power
in the battery 18 is lower than a predetermined limit. The
predetermined limit is set such that the robotic mower 2 may safely
return to the charging station 11 before the battery 18 is empty,
even if it happens to be the longest possible way back to the
charging station 11.
[0052] When the robotic mower 2 has received the command to return
to the charging station 11, it commences with mowing the area A
until it detects the boundary wire 4 by means of one or more of the
robotic mower's 2 sensors 12, 14 and 16 or 12, 14, 17 and 19,
respectively. When the boundary wire 4 has been detected, the
robotic mower 2 is controlled, in step S102, to follow the boundary
wire 4 at a fixed or random distance R.sub.d. The randomness may be
determined by a random generator in the control unit 22 each time
that the command to return the robotic mower 2 to the charging
station 11 is generated. Thus, the control unit 22 determines that
it is time to return to the charging station 11, generates a random
distance and sends a command to the robotic mower 2 to return and
which distance to the boundary wire 4 to use when returning. By
using different distances when the robotic mower 2 is to return to
the charging station 11 tracking in the lawn may be avoided.
[0053] The robotic mower 2 will follow the boundary wire 4 at the
random distance R.sub.d until detecting, in step S104, the charging
station loop 10 by means of at least one of the sensors 12, 14, 16,
17 or 19. In one embodiment the detection of the charging station
loop 10 is determined when one of the front sensors 12, 14 passes
the charging station loop 10. As a response thereto, the robotic
mower 2 is controlled, in step S106, by the control unit 22 to
follow the charging station loop 10, in a direction away from the
boundary wire 4, by using at least one sensor 12, 14, 16, 17, 19.
In one exemplary embodiment the robotic mower 2 is controlled, in
step S105 to move in a direction closer to the boundary wire 4
after detecting the charging station loop 10, such that the
docketing process may be better controlled. This is however
optional, as is indicated by the dotted lines in FIG. 7.
[0054] The robotic mower 2 will follow the charging station loop
10, including making a 90 degree turn as the charging station loop
10 turns 90 degrees, until a crossing between the charging station
loop 10 and the boundary wire loop 4a is detected, in step S108, by
means of the at least one sensor 12, 14, 16. The detection of the
crossing triggers the robotic mower 2 to follow the charging
station loop 10, in step S110, a first predetermined distance after
the detection of the crossing. This first predetermined distance is
long enough to straighten up the robotic mower 2 such that it runs
parallel with the charging station loop 10. When the robotic mower
2 has moved the first predetermined distance it continues, in step
S112, to drive the robotic mower 2 in a direction straight forward
for a second predetermined distance. After this step S112 the
robotic mower 2 is in a position that always will be the same and
that will ensure that the docketing between the robotic mower 2 and
the charging contacts in the charging station 11 will run
smoothly.
[0055] Thus, in this position the robotic mower will 2 be rotated
or turned a predefined angle towards the charging station 11, in
step S114, by means of the control unit 22. The robotic mower 2 may
also be turned until the front sensors 12, 14 pass the boundary
wire 4 towards the charging station 11. After the turn, the robotic
mower 2 is controlled, in step S116, to follow the boundary wire
loop 4a with at least one sensor 12, 14, 16, until a charging
position is reached. In an exemplary embodiment, the robotic mower
2 is provided with three sensors, two front sensors 12, 14 and one
rear sensor 16 and the detection of the charging station loop 10 is
then determined when one of the two front sensors 12, 14 passes the
charging station loop 10. As is understood by a person skilled in
the art there are many ways to use three or four sensors in order
to guide the robotic mower 2 during the docketing process. For
example, both front sensors 12, 14 may be used to control the
robotic mower 2, in step S116, to increase the accuracy when the
robotic mower 2 follows the boundary wire loop 4a to the charging
position. Furthermore, the width of the boundary wire loop 4a, may
be adapted to the actual distance between the two front sensors 12,
14, which will increase the robustness of the docketing
process.
[0056] If the robotic mower 2 is provided with four sensors 12, 14,
17, 19 instead steps S110 and S112 may be performed in a different
way. In step S110 the first distance is then reached when one of
the rear sensors 17, 19 is at a known position in front of the
charging station 11, for example when one of the rear sensors 17,
19 reaches the charging station loop 10. In step S112 the second
distance is then reached when one of the rear sensors 17, 19 is at
a known position in front of the charging station, for example when
one of the rear sensors 17, 19 reaches the boundary wire loop 4a.
These alternative steps are shown in FIGS. 5h and 5i.
[0057] Turning now to FIG. 6a to FIG. 6d and FIG. 8 another
exemplary embodiment of the method according to the present
invention will be closer described. The difference between the
previous described method and this method is that the later one
uses a guide wire 8 to return to charging station 11 instead of
boundary wire, which enables a shorter return time for the robotic
mower 2 when it returns to the charging station 11. The method
starts in step S200 in which the robotic mower 2 receives a return
signal from the control unit 22, which commands the robotic mower 2
to return to the charging station 11. As mentioned above the return
signal may be triggered by detecting that the power in the battery
18 is lower than a predetermined limit. However, there may also be
other trigger events, such as a rain sensor that has detected
rain.
[0058] When the robotic mower 2 has received the command to return
to the charging station 11, it commences with mowing the area A
until it detects the guide wire 8 by means of one or more of the
robotic mower's 2 sensors 12, 14 and 16. When the guide wire 8 has
been detected, the robotic mower 2 is controlled, in step S202, to
follow the guide wire 4 at a random distance Rd. As mentioned
above, the randomness may be determined by a random generator in
the control unit 22.
[0059] The robotic mower 2 will follow the guide wire 8 at the
random distance Rd until detecting, in step S204, the charging
station loop 10 by means of at least one of the sensors 12, 14, 16.
In one embodiment the detection of the charging station loop 10 is
determined when one of the front sensors 12, 14 passes the charging
station loop 10. As a response thereto, the robotic mower 2 is
controlled, in step S206, by the control unit 22, to move closer to
the guide wire 8. This is done to ensure that the robotic mower 2
will cross the boundary wire loop 4a, when continuing to follow the
guide wire 8. Thus, how close to the guide wire 8 the robotic mower
2 has to be moved is decided by the width of the boundary wire loop
4a.
[0060] The robotic mower 2 continues to follow the guide wire 8 at
a closer distance until it is detected by means of the at least one
sensor 12, 14, 16, in step S208, that the robotic mower 2 passes
the boundary wire loop 4a. Thereafter, the robotic mower 2 is
controlled, in step 210, to follow the boundary wire loop 4a with
at least one sensor 12, 14, 16 until a charging position is
reached.
[0061] As mentioned above, there are many ways to use three sensors
12, 14 and 16 in order to guide the robotic mower 2 during the
docketing process. For example, both front sensors 12, 14 may be
used to control the robotic mower 2, in step S210, to increase the
accuracy when the robotic mower 2 follows the boundary wire loop 4a
to the charging position. Furthermore, the width of the boundary
wire loop 4a, may also in this exemplary embodiment be adapted to
the actual distance between the two front sensors 12, 14, which
will increase the robustness of the docketing
[0062] Although, the present invention has been described above
with reference to specific embodiments, it is not intended to be
limited to the specific form set forth herein. Rather, the
invention is limited only by the accompanying claims.
[0063] In the claims, the term "comprises/comprising" does not
exclude the presence of other elements or steps. Furthermore,
although individually listed, a plurality of means or elements may
be implemented by e.g. a single unit or processor. Additionally,
although individual features may be included in different claims,
these may possibly advantageously be combined, and the inclusion in
different claims does not imply that a combination of features is
not feasible and/or advantageous. In addition, singular references
do not exclude a plurality. The terms "a", "an", "first", "second"
etc. do not preclude a plurality. Reference signs in the claims are
provided merely as a clarifying example and shall not be construed
as limiting the scope of the claims in any way.
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